diff --git a/src/debug.cpp b/src/debug.cpp
--- a/src/debug.cpp
+++ b/src/debug.cpp
@@ -220,22 +220,14 @@ void SetDebugString(const char *s, void 
  * Just return a string with the values of all the debug categories.
  * @return string with debug-levels
  */
-const char *GetDebugString()
+std::string GetDebugString()
 {
-	const DebugLevel *i;
-	static char dbgstr[150];
-	char dbgval[20];
-
-	memset(dbgstr, 0, sizeof(dbgstr));
-	i = debug_level;
-	seprintf(dbgstr, lastof(dbgstr), "%s=%d", i->name, *i->level);
-
-	for (i++; i != endof(debug_level); i++) {
-		seprintf(dbgval, lastof(dbgval), ", %s=%d", i->name, *i->level);
-		strecat(dbgstr, dbgval, lastof(dbgstr));
+	std::string result;
+	for (const DebugLevel *i = debug_level; i != endof(debug_level); ++i) {
+		if (!result.empty()) result += ", ";
+		fmt::format_to(std::back_inserter(result), "{}={}", i->name, *i->level);
 	}
-
-	return dbgstr;
+	return result;
 }
 
 /**
diff --git a/src/debug.h b/src/debug.h
--- a/src/debug.h
+++ b/src/debug.h
@@ -58,7 +58,7 @@ extern int _debug_random_level;
 
 void DumpDebugFacilityNames(std::back_insert_iterator<std::string> &output_iterator);
 void SetDebugString(const char *s, void (*error_func)(const std::string &));
-const char *GetDebugString();
+std::string GetDebugString();
 
 /* Shorter form for passing filename and linenumber */
 #define FILE_LINE __FILE__, __LINE__